[dandlift]

Agree, I also find useful to split between domain concerns and application concerns.

A report is something that belongs to business, but the fact that it could be sent via email is totally accidental and depending on the technology we use (as it is the persistence layer, or the protocol which exposes the app).

Domain concerns live on domain object (which knows only other domain objects), while application concerns live in services. And here is where you have interfaces, concrete implementations and, where necessary, factories to switch or add the implementation at the flip of a switch. Eg: a ReportMailSender which implements a ReportSender, that someday get replaced with a SlackSender implementing the same interface. You want both? Wrap them on a AggregatedSender.

Now your DI framework is getting really useful.